Optic flow sensor with negative iris photoreceptor array

• US 6,683,678 B2
• Filed: 10/24/2002
• Issued: 01/27/2004
• Est. Priority Date: 09/28/2001
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Barrows, Geoffrey
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US10/278,862
• Publication Number:
  US 20030076486A1
• Time in Patent Office: 460 Days
• Field of Search: 356/28, 250/237.R
• US Class Current: 356/28
• CPC Class Codes: G01P 5/001 Full-field flow measurement, e.g. determining flow velocity and direction in a whole region at the same time, flow visualisation
• CPC Class Codes: G06T 7/269 using gradient-based methods

Abstract

An improved optic flow sensor is provided which affords enhanced bandwidth without the use of a lens. A plurality of photoreceptor circuits, arranged in a linear array, sense light received from a visual field and produce a plurality of photoreceptor signals in accordance with the light sensed. A negative iris, disposed between the visual field and the photoreceptor circuits, blocks a portion of the light from the visual field so that the light blocked by the negative iris is not received by the photoreceptor circuits. The photoreceptor signals are used in determining optic flow in the visual field. The invention is useful for implementation using micro electromechanical system (MEMS) techniques.

Claims

1. An optic flow sensor comprising:

a plurality of photoreceptor circuits for sensing light received from a visual field and for producing a plurality of photoreceptor signals in accordance with the light sensed, said photoreceptor circuits being arranged in a linear array;

a negative iris disposed between the visual field and the photoreceptor circuits for blocking a portion of the light from the visual field so that the light blocked by the negative iris is not received by the photoreceptor circuits; and

a contrast level enhancor for receiving the photoreceptor signals and for enhancing the contrast levels of the photoreceptor signals; and

an optic flow determinator responsive to said photoreceptor signals for determining optic flow in the visual field.

2. An optic flow sensor according to claim 1 wherein said negative iris comprises a rectangular light blocking element.

3. An optic flow sensor according to claim 1 wherein said photoreceptor circuits comprise rectangular photoreceptors.

4. An optic flow sensor according to claim 3 wherein said rectangular photoreceptors extend parallel to said rectangular iris.

5. An optic flow sensor according to claim 1 wherein said negative iris comprises a plurality of light blocking elements.

6. An optic flow sensor according to claim 5 wherein said light blocking elements are rectangular in shape.

7. An optic flow sensor according to claim 1 wherein said negative iris comprises a substantially point shaped light blocking element and said photoreceptor circuits comprise rectangular photoreceptors.

8. An optic flow sensor according to claim 1 wherein said negative iris comprises a colored iris element for blocking a sub-band of white light.

9. An optic flow sensor according to claim 1 wherein the contrast level enhancor comprises a circuit for receiving the photoreceptor signals, for computing a mean value for the photoreceptor signals and for computing, for each photoreceptor circuit, the difference between the photoreceptor signal for that photoreceptor circuit and said mean.

10. An optic flow sensor according to claim 1 wherein the optic flow determinator comprises a plurality of feature detectors for receiving said photoreceptor signals and said contrast level enhancing means comprises amplifying means for increasing the amplification of said feature detectors.

11. An optic flow sensor according to claim 1 wherein said optic flow sensor is implemented in micro-electromechanical systems technology and said negative iris comprises an etched iris structure.

12. An optic flow sensor comprising:

a plurality of photoreceptor circuits for sensing light received from a visual field and for producing a plurality of photoreceptor signals in accordance with the light sensed, said photoreceptor circuits comprising photoreceptors defining a sensor orientation vector, said photoreceptors each having a response function of a rectangular shape defining a longitudinal axis extending perpendicular to said sensor orientation vector, and being arranged in a linear array;

a negative iris of a rectangular shape, disposed between the visual field and the photoreceptor circuits and extending perpendicular to said sensor orientation vector, for blocking a portion of the light from the visual field so that the light blocked by the negative iris is not received by the photoreceptor circuits;

a contrast level enhancor for receiving the photoreceptor signals and for enhancing the contrast levels of the photoreceptor signals; and

optic flow determinator responsive to said photoreceptor signals for determining optic flow in the visual field.

13. An optic flow sensor according to claim 12 wherein said negative iris comprises a colored iris element for blocking a sub-band of white light.

14. An optic flow sensor according to claim 12 wherein the photoreceptors signals have contrast levels and said sensor further comprises a contrast enhancor for enhancing the contrast levels of the photoreceptor signals.

15. An optic flow sensor according to claim 12 wherein the contrast level enhancor comprises a circuit for receiving the photoreceptor signals, for computing a mean value for the photoreceptor signals and for computing, for each photoreceptor circuit, the difference between the photoreceptor signal for that photoreceptor circuit and said mean.

16. An optic flow sensor according to claim 12 wherein the optic flow determinator comprises a plurality of feature detectors for receiving said photoreceptor signals and said contrast level enhancor comprises amplifying means for increasing the amplification of said feature detectors.

17. An optic flow sensor according to claim 12 wherein said optic flow sensor is implemented in micro-electromechanical systems technology and said negative iris comprises an etched iris structure.